1. Field of the Invention
The present invention generally relates to an optical imaging lens. Specifically speaking, the present invention is directed to an optical imaging lens for the application of dual band of visible light as well as NIR (near infrared) for use in portable electronic devices such as mobile phones, cameras, tablet personal computers, personal digital assistants (PDA), vehicles, or rescue devices for recording videos.
2. Description of the Prior Art
The applications of an optical imaging lens is not only limited to take pictures and to record videos but also for the environmental surveillance, the dashboard cameras, the VR trackers or the face recognition. With the increasing applications, one single device may need to install at least one visible light imaging lens as well as an NIR imaging lens at the same time. Such demands for the double imaging lens sets not only increase the cost as well as the complication of the device but also influence the appearance design of the device.
The first thing to overcome in order to design a dual band optical imaging lens is to solve the problem of respective focusing of different wavebands. When the object distance changes, the voice coil motor (VCM) in the lens set module makes the position of the sensor change to focus. When the light has different wavebands, the sensor has different position to focus.
It is a main pending problem to design a dual band optical imaging lens and to go with a sensor of RGB & IR wavebands to capture the imaging rays of RGB & IR light at the same time and to simultaneously focus all light at the same plane. In addition to solving these problems of simultaneous focusing and to maintain good imaging quality at the same time, the half field of view is also needed to be larger for the detection of larger space.
However, a larger half field of view not only lowers the imaging quality but also jeopardizes the focusing ability of the dual band rays. In accordance with the above prior art, it is another issue to increase the half field of view for the design of the dual band optical imaging lens.